This invention relates to ballast sweepers for sweeping the ballast on railroad tracks. More specifically, this invention relates to dust control for such ballast sweepers.
The use of ballast sweepers in connection with maintenance of a railroad track is well known. Commonly, a plow or blade-like element is used to shape or distribute the ballast in a desired arrangement. However, when ballast is plowed or new ballast is dumped onto a railway roadbed, ballast may become disposed upon the tops of the railroad ties.
In order to evenly distribute the ballast and clear ballast from the tops of the railroad ties, it is common to use a railroad maintenance machine having a rotary sweeping core with a plurality of sweeper elements or bristles such as disclosed in the present inventor's prior U.S. Pat. No. Re. 31,619 issued Jul. 3, 1984 and hereby incorporated by reference. That patent describes a particular sweeper element or bristle and a method of making it. The rotary core may be mounted on the same machine as the plow blade.
The ballast is usually a thick layer of crushed limestone placed between and along side of the rails. As will be readily appreciated, the sweeping of the limestone from off the tops of the ties generates a very large amount of dust. The dust creates very harsh conditions such that the air filter on the engine which propels the broom or sweeper machine along the tracks must be replaced very often. Further, the dust covers and damages other parts of the vehicle.
More important than the effect of the dust on various parts of the maintenance vehicle having a rotary sweeper, the dust creates undesirable conditions for the operator riding on the vehicle. In addition to the discomfort associated with large amounts of dust falling on the clothing of the machine operator, there is some concern over potential health problems. Preferably, the operator will wear a dust mask to minimize the amount of dust which might otherwise be inhaled, but wearing such a mask is often uncomfortable.
Another problem created by the dust is that the amount of dust created by operation of such machines may lead to problems with government environmental regulators.
In order to minimize the problem of dust in connection with such machines, at least two different approaches have been proposed. A first approach has been to use a fan to remove air, by way of a filter, from within a housing in which the rotary sweeper is disposed. Dust within the air being removed from inside the housing builds up on the filter elements very quickly. Accordingly, the filter elements are sequentially backwashed by applying a high pressure air blast against the normal flow of air through the filter such that debris on the filter will fall into a hopper from which it can be periodically released. Since a large amount of dust is deposited on each filter between the periodic blast of backwashing air, the filter elements tend to wear out relatively quickly. Additionally, it is generally disadvantageous to have to provide a hopper to catch the dust and to take the time to periodically release the dust from the hopper. Finally, even with this technique of filtering air removed from the housing in which the broom's rotary core is disposed, a significant amount of dust may escape from the bottom periphery of the housing.
The arrangement of using filters with rotary broom machines and backwashing the filters is disclosed in one or more of the following U.S. patents issued to David Franklin Howeth and which are hereby incorporated by reference: U.S. Pat. Nos. 4,802,983; 4,756,727; 4,708,723; and 4,650,504. The U.S. Pat. No. 4,802,983 patent has a hopper to catch the dust which was blown off the filters by a backwashing air blast as discussed.
A second approach which has been considered is to use a spray of water against the dust such that it will fall back to the ground. However, the amount of dust which is generated is so large that a great amount of water must be used. A water reservoir must be located on the machine and the water adds substantial weight to the machine. If one attempts to reduce the weight by using a smaller reservoir or water tank, the water must be replaced quite often.
U.S. Pat. No. 5,172,638 issued to Mathison et al on Dec. 22, 1992 relates to a dust suppression system using a liquid spray to reduce dust for a ballast cleaning apparatus. The ballast cleaning apparatus is used to break up and clean ballast which may have been cemented together by water, mud, and other conditions.